Gloss imparting method, image forming method, fixing apparatus and image forming apparatus

00 A gloss-imparting method that includes (a) applying heat and pressure to one side of a recording material having an image of toner formed on both sides, and fixing the image to the one side of the recording material; (b) cooling the one side of the recording material; (c) applying heat and pressure to the other side of the recording material, and fixing the image to the other side of the recording material; and (d) cooling the other side of the recording material, in the step (a), the fixing being performed such that a value of exp(−T·tan δ) will be approximately 0.85 or less, where tan δis a loss tangent of the toner when measured by dynamic viscoelastic measurement at a frequency of approximately 1 rad/sec at approximately the same temperature as a fixing temperature of the step (a), and T is a fixing time in the step (a).